Articulated blade propeller



Aug 11, 1953 M. E. CUSHMAN f-:T AL

ARTICULATED BLADE PROPELLER 5 Sheets-Sheet 2 Filed March 14 1951 HMAN 4* mwa-E Aug. l1, 1953 M. E. cUsHMAN ETAL 5 Sheets-Sheet I5 Filed March 14, 1951 n IN ENTOR` E CUSHMAN* KIEFER JI? UmcE PAUL J Patented Aug. 11, 1953 LRTCUULATED BLADE PROPELLER Maurice E. Cushman, Verona, and Haul J. Kiefer, Jr., Clifton, N. J., assignors to Curtiss-Wright Corporation, a corporation of Delaware Application March 14., 1951, Serial No. 215,418

lll Claims.

This invention relates to aeronautical propelu 1ers and is concerned particularly with an arrangement for mounting the blades of a propeller in a hub in such a manner that the blades are controlled for pitch change but otherwise are free to articulate universally to minimize bending moments in the propeller blades and hub.

While articulated propeller blade mountings have been taught broadly in the prior art, the structural features involved in known mcuntings have many disadvantages from the standpoint of weight, strength and complication. Still, a structurally adequate articulated blade mounting holds considerable promise for weight re duction in a propeller. lf the bending moments in the propeller blade are materially reduced by articulation, the amount of material in a propeller blade may be lessened 'with consequent lightening thereof, with consequent reduction in the centrifugal force imposed on the rotating propeller blade which again enables a weight reduction in the blade. A propeller blade in operation is stabilized in a generally radial direction in its hub by the action of centrifugal force. Other forces imposed on the blade in operation include aerodynamic and vibratory loadings, torque loading, and thrust loading. These latter loadings tend to make the propeller blade depart from a normally radial position.. If the blade mounting is so constructed so as to allow of such departure rather than having the blade rigidly mounted, the position of the lade in operation will still be effective for aircraft propulsion while permitting the above in dicated minimization of stresses in the propeller blade and also in the propeller hub.

It is a particular object of this invention to provide a propeller blade mounting in a propeller hub which allows limited universal movement oi the propeller blade with respect to a radius o' the propeller hub normal to the propeller rotational axis. The blade may tilt forwardly or rearwardly from the plane of rotation and may tilt in advance or in retard of a hub radius with respect to the direction oi hub rotation. Also, the blade may move in any coinbination or the above two modes of movement. t is a further object of the invention to provide a mounting wherein the blade 'will be constrained to a controlled pitch position regardless of the direction and magnitude of the aforesaid blade tilting.

To accomplish the above objectives, a more or less conventional propeller blade is secured (Cl. IWB-150.52)

in a propeller hub socket by means of an antifriction universal joint of spherical configuration l which is capable of assuming the radial centrifugal loading on the propeller blade and other forces imposed on the blade. rlhe joint, brielly, comprises two arrays of small barrel-shaped rollers oriented to provide intersecting rocking axes for the joint at 90 degrees to one another, the rollers being disposed between sets of hardvened steel races having spherically segmental conguration. The invention further includes the provision of retainers to hold the rollers in their best orientation and includes means to. urge the retainers and rollers toward a con trolled position relative to the socket axis so that they cannot drift away from the position where full bearing capacity is assured.

Additional objects of the invention will be appreciated from reading the annexed detailed description in connection with the drawings, and it is to be understood that the description and drawings reveal only a single embodiment of the invention. The scope of the invention. is as broad as the sub-joined claims will permit.

In the drawings, wherein similar reference characters indicate similar parts,

Fig. l is a fragmentary longitudinal section through a portion of a propeller embodying the invention;

Fig. 2 is a fragmentary section on the line 2-2 of Fig. 1;

Fig. 3 is a partial plan view of a developed multiple roller bearing retainer used in the invention showing a preerred disposition of the rollers;

Fig. 4 is a fragmentary View of one of the roller bearing race assemblies wherein the races are offset relative to one another at the maximum angularity of articulation of the blade with respect to its hub; and

Fig. 5 is a diagram of the arrangement of roller bearings in the invention.

A propeller hub is indicated at 5 and is provided with a plurality of blade sockets one of which is indicated at l. The hub, in convenn tional manner, is provided with a bore 8 equipped with internal splines S by which the propeller may be mounted on a suitable propeller shaft. ln the recess Ill of each socket 'l is a platform ii providing a positioning point for a propeller blade I2 secured within the socket. The blade at its inner end is provided with an integral flange it against which is seated a member I5 having a spherical end i6, this spherical end engaging a cup ll whose inner end rests against the seat I I. Also, the cup I1 is secured to other parts of the structure, to be described, by a Belleville washer I8 to hold the bearing system up to the race 28 in assembled relation with the blade and cup. The member I has a spline connection I9 with the interior of the blade I2 to constrain the member I5 and the blade I2 for rotation wit'honeanother.

Embracing the exterior of the inner end of the blade I2 and resting against the ange I4 is a race member 20, the member being split on a diameter for assembly over the blade shank-.and being formed exteriorly with a spherical surface 2| whose center is the center 22 of thefball I6.

Embracing the race 20 is a `fl'rst intermediate annular race 24 which is spherically'jformed'at its inner surface 25 and at its outer surface .26, both of these surfaces 25 and 26 also being struck from the center 22. Therace surfaces'2I and 25 provide for longitudinal rocking or articulation of the bladeabout a first axis substantially; normal tothe socket axi-s, passingthrough` .the center 22. Furtherembracing the race member 24 vis va second intermediate race member v28 whose inner surface 29 is-spherically'formed from the center 22 and whose outer surface 30' vis formed as'a coneewith a plurality ofannular'ball races 3I, these grooves being concentric .with the socket. The race surfaces 26. and'291provide for rocking or articulationv ofthe blade about an axis normal to the socket axis andnormal to said 'rst a'xis 4parallel tov the *propeller Vshaft and passing through the center f2.2.

Screwed within the outer endl of the'hub socket 'I is an outer race -32 formedexternally as an internal nut to engage the socket II'at threads 33 to .secure the bearing .assembly within `the socket, and formed at 34-`as an internally conical bearing race having annular groovesV 35fcornplementaryto the lannular'l groovesfSI of the raceY 28 and concentric with the socket. Between the annular grooves 35 and v3I are a plurality of bearing balls 31 retained `i'nfconical shell-'like retainers 38, enabling the race`f28to move freely, with respect to the hub socket.

YRoller and ballbearings, to bedescrib'ed, are disposed between the races V2'Il.an`d-'24, and between the races 24 and 28fso' that :the blade proper along with the said races are all con-Y strained torotate in unison relative to thesocket.

Rotational position of this assembly-about the blade axis establishes lthe pitch setting of the propeller blade and is accomplished by. an adapter 39'splined 'at'40 tothe race-28 and splined at 4l to a blade gear 42 controlled in its posif,-

tion by an appropriate pitch changing mechanism, not shown.` Theblade gear holds the rim of the washer I8 andis secured "totheadapter 39; the adapter v39,-is-secured to' the :race 2S by screws in addition to the spline connection '40. The pitch changing-mechanism, as is well known in the art, is adapted to controlthepitch of a number of propellerfblade's simultaneously vand may include a master gear, concentricwithv the propeller shaft, engaging the gears '42 on the several blade assemblies of thel propeller..

The lgears 42 land 'the above suggested. master gear are merely exemplaryv cfa means for connecting the pitch changing mechanism to v.the blades. These are' not intended `to limit the scope ofthe invention.

Between the races 20-"and'24 are disposed al large plurality'` of short bearing rollers, the rollers being arranged so that asxlarge as possible anarea of the two races are covered by the rollers.

Fig. 3 shows a developed plan of the arrangement of rollers each carrying the designation 44, the rollers being retained in a shell-like an nular member 45. These rollers enable the race 20 to rock with respect to the propeller hub in the fore-and-aft plane. The races 2f) and 24 are locked against relative rotation about the axis of the; propeller blade -by rows of balls 4B shown in Figs. 1 and 3 which are larger in diameter than the rollers 44 and which seat in grooves '50 in the races 20 and 24, the grooves being segments of-a great circle on the spherical surn faces of the races.

The orientation of the rollers 45s on the race surfaces and in the retainer 46 is important. Inorder to roll with minimum sliding or scrub bing onthe spherical race surfaces, the axis of each roller must intersect the appropriate axis of articulating rotation, passing through the sphere center 22 and normal to the plane occupied by the keying balls 48. Such articulating axis is noted in Fig. 3 at 49 for'the rollers 44; the articulating axis for the other set of rollers 44"lies at a right angle to the axis 43. Each roller 44 `rolls in a plane' parallel to the plano lobtained ifthe race surfaces A2|, 24' werefcylindrical, with the race surfaces 26, 29 also cylindrical but with the 'cylinder axis oriented at a right angleto the axis of cylindrical surfaces 2l, 24'; But if the bearing assembly were so constructed, a great increase in mass and bulk would result,.making the joint arrsmgement-imn practical for aeronautical propeller' use.V Also roller orientation problems could be obviated by substituting balls for `the rollers 44. Rollers, however, have agreater load capacity, and are preferred since the centrifugal loading on the bearings is high, due torotation loi the propeller about the axis of the propeller hub.

In the samemanner as'described above, rollers 44 arev disposed between the facing spherical surfaces `26-and29 of the races 24 andZ, the

rollers being retained in. an annular disc-1ike retainer 48. The rollers 44 are oriented to enable swinging `of the propeller vblade with revspect to the socket transversely to the propeller axis, or inthejplane of rotation of the propeller. As 1n the previously described arrangement, balls 48 lock the races 28 and 24 from yrelative rotation-about the propeller blade axis, these keying balls 48' shown in Fig. 2, engaging great circle tracks 50' in the spherical faces 26 and 29 of the races 24 and 28.

In. Fig. 3, the annular roller retainer 46 is shown as-though it were planar, with the rollers 44 1n axially parallel rel-ation and parallel to the rockingV axis49. When this retainer is cupped into spherically segmental form to occupy its proper position between the spherically segmental roller races, eachI individual` roller, and the cutout in the retainer in which each roller is disposed, is reoriented so that each rollei1 axis will intersect the axis 49 as shown in Fig. 5. Thereby, each roller will roll Without substantial endwise `sliding in -a .circular path parallel. to equatorial circle of the sphere. The keying balls 48 roll in a segment of theequatorial circle,

The race 28 as indicated previously, mayrotate about the axis of the propeller blade on the bearing balls 31 under the influence of the gear 42 to .effect pitch change of the propeller blade.

This is shown diagrammatically in Fig. 5.-

When the race 28 is so rotated, pitch changing rotation is imparted to the race 2) through the balls 48 and 48 and thence through spline connections 52 and 54 from the race 2G to the adapter i5 and thence to the blade 20 through the spline connection I9. The two sets of rollers 44 and 44 provide large bearing area to sustain the centrifugal force imposed upon the blade in operation while allowing free universal action of the blade for articulating purposes. Each roller 44 and 44 is slightly barrel 'shaped so that it will have substantially line contact on the inner spherical surfaces of the races 28 and 24.

Fig. 3 shows the pattern of rollers to enable rocking of the related races with respect to one another so that there will always be rollers between the coacting race faces. For instance, if one ra-ce is rocked with respect to the other race as is shown in Fig. fl, a portion of each race will overhang the other, but the overlapped race portions will be adequately provided with loaded rollers. It will be noted in the zone 55 in Fig. 3 that the overall span of the rollers is less than the overall span at 5S. This is necessary7 to avoid rollers leaving one of the races when the races are overlapped relative to each other.

Since the sets of rollers 44 and 44 lie between race surfaces which have oscillatory motion with respect to each other and since the race surfaces vare not complete annuli, it is necessary to ref strain the roller retainers 46 and 46 so that they will not creep out of their correct relationship with the coacting race surfaces during operation of the propeller. The retainers could be positively held to their proper orbit. Preferably, they may at all times be urged toward a correct position between the races by elastic means which impose a force upon them. The retainer 45 is provided with ears Si) extending beyond the roller carrying portions thereof, these ears being disposed on a great circle aligned with the keying balls 48. The outer end of each ear 60 is inwardly formed as at 52 with a wedge arrangement, and springs 63 and 64 are disposed on either side of the wedge @2. The spring 63 acts between the wedge $2 and the inner race 2D, while the spring 64 acts between the wedge 62 and a socket carried by the adapter 39. The opposed sets of springs as noted in Fig. 1 continuously tend to hold the retainer 46 in a position such that the rollers and balls 44 and 4i! will lie in contact with the races, the retainer shifting angularly through half the angle of race shift.

In the saine manner, the retainer 46 as shown in Fig, 2 carries ears 63 terminating in wedges 62. Springs 63 and 64 respectively act between portions of the race 2B and wedge, and between the wedge and sockets 66 carried by the adapter 59. The two pairs of springs 63, 64 and E3', Eil', at right angles relative to the blade, serve to urge the retainers, balls 48, 48 and rollers 4st, 44 to their proper positions along their respective rectilinear lines of action.

Since the hub system contains lubricant, sealing provisions to prevent the escape of lubricant are required for the articulating mechanism. To this end, a resilient boot E3, of annular form, is provided for each blade, one end of the boot having a bead E9 secured to the blade shank by an annular ring lil, and the other end of the boot being beaded at "H and being secured to the intermediate race 28 by a ring 12 and splines 13. A portion of the bead 'H engages a flange 'I4 on Cil the retaining nut 32 in sliding sealing engagement. The spline connection 13 enforces the sealing boot 68 to rotate with the propeller blade when pitch changes are made so that the boot is not twisted.

The blade retaining nut 32, when properly screwed into the hub socket 'I to provide firm contact of all of the bearings, and to seat the b-all I6 on the socket I1, is held in place by locking lugs and screws 16 securing the blade nut 32 against rotation relative to the socket 1.

Other seals of more or less conventional character are provided in the system where necessary. For instance, a seal ring 11 is disposed between the member l5 and the blade shank to prevent lubricant leakage into the blade hollow; also a seal ring 18 is provided between the blade nut and the socket to prevent leakage through the threads 33.

From the structure described it will be seen that the propeller blade I2 may articulate in its socket about the center 22 through limited angles, either in the plane of rotation or in the direction of night or in any combination of these two modes of motion. This articulation has complete freedom with minimum friction and virtually no restraint. The amount of articulation may be of the order of about 8 degrees as noted by the dotted line outline of the propeller blade in Fig. 2. Limits of articulation are established by a bumper flange 8o on the propeller blade shank which at the limit of articulation may contact the inner edge of the outer race 28 as at 82. As has been shown in the prior art on articulated blade mountings, elastic bumpers may be used in the system at the limit of blade articulation, if desired.

A further point in the construction herein shown is that blade drive for pitch change is accomplished without introducing motion errors or restraint to articulation. In the construction of the various bearing retainers previously described, suitable devices may be used, in a-ccordance with usual practices in the bearing art, for holding the various rollers and balls in the retainers so that they will not drop out if the race surfaces become separated as during assembly and disassembly of the mechanism.

Though but a single embodiment illustrating the invention has been shown and described, it 1s to be understood that the invention may be applied in other and various forms. Changes may. be made in the arrangements, without departing from the spirit of the invention. Reference should be had to the appended claims for definitions of the limits of the invention.

We claim:

l. .An aircraft propeller comprising a hub including a socket extending' radially outwardly from the hub an inwardly facing race secured within said socket, a second race having an outer surface in thrust bearing relation to the first race and rotatable relative thereto about the socket axis and having an inner face of spherically segmental form, a propeller blade in said socket having a shank passing through said races and having at its inner end an outwardly facing spherically segmental blade race, a plurality of rollers between and in rolling engagement with said spherically segmental race surfaces enabling articulation of said blade relative to said socket, keying means engageable with and between the second race, the blade race and blade to enforce joint rotation thereof about the socket axis, and means drivably connected to menacer;

turni said second race; to Y' effect changes ,f infV pitclrI of, the fpropeiler.. blade;

2.` A11-'aircraft propeller. comprisinggahub in cluding, a, socket extending radially outwardly from the hub axis, an inwardly facing: race-securedw-ithin.' said socket, ai. second race having an outersurfacein` thrustV bearing relation to the-first race and rotatable relative thereto about the. socket axis and' having an inner face of spherically segmental form, a propeller blade in said sockethaving a-.shank passing through said raccsand. havingat its inner end-an outwardly facingspherica'lly.l seg-mentalfblade race, a plurality.v of rollersbetween andinrolling engagement with:l said. spherically segmental race -surfaces enablingv articulation .of said.. blade relative to saidsoeket, keyinggmeans engageable with and between .the second race, the blade race and blade to enforce joint rotation thereof about the socket. axis, means drivably connected to turn saidsecond raceto effect changes in pitch ofthepropellerv blade, a cageholding saidrollers in, spaced relationto. one another and lying betweensaid spherically segmental racesurfaces,

stacked uponioneanother, one of saidracesbeing. secured to the blade and a second race outwardlythereof being journalledin saidV socket for rotation relativethereto aboutthe hub axis, anti-frictionthrust rollers disposed between said races.means engaging said races to constrain them torotation in.unison, and means to rotatev said..second race about the socket. axis to impart pitchlchange Vto the blade.

4. InE an aircraft. propeller comprising a. hub having. a; socket, extending radially outward therefrom` and abladedisposed in said-socket,

bearing means between the hub and the inner end of said blade defining aV pivotcenter for articulationof the blade with respect-to the hub, a plurality of spherically segmental annular races stacked uponone another, one of said races beingsecured to. the blade and a, secondv race outwardly` thereof .being journalled in said socket for. rotation relative thereto. about the socket axis, anti-.friction thrust rollers disposed. between said races, said stack of races including-an intermediaterace between the two mentioned, means engaging said racesto constrain them to rotation in unison, means to rotate thesecond raceaboutthe socket axis to impart pitch change.

to the blade, the rollers between the bladesecuredv race and the intermediate race being oriented for swinging of the bladeabout one axis normal to the socket axis, and the rollers between the intermediate race and said second race being oriented for swinging ofthe blade about anotherv axis normal to the socket'axsand normal to said one axis.

5. In an aircraft. propeller, -ahub having a socket extending radially outward therefrom, a blade having an enddisposed in said-socket,. an

articulating. bearingY securing the blade in said socket comprisinga, firstv inwardly facing spherically `segmental race secured within the socket,

socket axis, said bearing comprising an outer ant outwardly, facing.; spherically segmental. race secured-tdtheblade and lying inwardly of thel first; race,..both -ofv said races being annular and blade having. an. end disposed in said socket, an.

articulating. bearing securing the blade in said socketallowing blade articulation about first and.

second relativelyangled axes normal to theblade socket axis, said bearing comprising an outer raceannular member carried by the socket and rotatable aboutthe socket axis andhaving an inwardly facing .first race surface concentric with saidV iirst axis, an intermediate race member having an outer race surface concentric with said rst, axis and facing said first race surface and an inner racesurface concentric with said second axis, an inner annular race member embracing and securedv to said blade having an outer race surface concentric with said second axis and facing said inner race surface, roller means between said outer and intermediate race members, and between said intermediate and inner race members, and means to retain said roller means between and in engagement with respective race members.

7. In an aircraft propeller, a hub having a socket extending radially outwardly therefrom, a blade havingan end disposed in said socket, an articulating bearing securing the blade in said socket allowing'blade articulation about first and secondA relatively angled axes normal to the blade socket axis, said bearing comprising an outer race-annularmember carried by the socket and rotatable about the socket axis and having an inwardly facing rst` race surface concentric with said rst axis, an intermediate race member having an outer race surface concentric with said first axis and facing said first race surface and having an inner race surface concentric with saidA second axis, an inner annular race member embracing and secured to said blade .having an outer race surface concentric with a blade'hav'ing an end Ydisposed in said socket, anA

articulating A bearing securing the blade in said socketallowing blade articulation about first and second relatively angled axes normal-to the blade raceannular member carried by the socket rotatable about the socket axis and having an inwardlyl facing rst race-surface concentric with saidV first. axis, an intermediate race member having an outer race surface concentric with said first axis and facing said first race surface and having, an inner race surface concentric with said second axis, an inner annular race member embracing and secured to said blade having an outer race surface concentric with said second axis and facing said inner race surface, roller means between said outer and intermediate race members, and between said intermediate and inner race members, means to retain said roller means between and in engagement with respective race members, said retaining means being annular in form and embracing the blade, and elastic means acting between the retaining means and the associated race members urging said retaining means to a controlled position between the race members between which the retaining means is disposed.

9. In an aircraft propeller, a hub having a socket extending radially outwardly therefrom, a blade having an end disposed in said socket, an articulating bearing securing the blade in said socket allowing blade articulation about first and second relatively angled axes normal to the blade socket axis, said bearing comprising an outer race annular member carried by the socket rotatable about the socket axis and having an inwardly facing rst race surface concentric with said first axis, an intermediate race member having an outer race surface concentric with said rst axis and facing said first race surface and having, an inner race surface concentric with said second axis, an inner annular race member embracing and secured to said blade having an outer race surface concentric with said second axis and facing said inner race surface, roller means between said outer and intermediate race members, and between said intermediate and inner race members, and means to retain said roller means between and in engagement with respective race members, said race surfaces all comprising spherical segments having a common center.

10. In an aircraft propeller, a hub having a socket extending radially outwardly therefrom,

ll fi a blade having an end disposed in said socket, an articulating bearing securing the blade in said socket allowing blade articulation about first and second relatively angled axes normal to the blade socket axis, said bearing comprising an outer race annular member carried by the socket rotatable about the socket axis and having an inwardly facing first race surface concentric with Said rst axis, an intermediate race member having an outer race surface concentric with said rst axis and facing said first race surface and having, an inner race surface concentric with said second axis, an inner annular race member embracing and secured to said blade having an outer race surface concentric with said second axis and facing said inner race surface, roller means between said outer and intermediate race members, and between said intermediate and inner race members, means to retain said roller means between and in engagement with respective race members, said race surfaces all comprising spherical segments having a common center, the rollers between the outer and intermediate members having their respective axes intersecting the first of said articulation axes, and the rollers between the intermediate and inner members having their respective axes intersecting the second of said articulation axes.

MAURICE E. CUSI-IMAN.

PAUL J. KIEFER, JR.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 2,230,811 Pecker Feb. 4, 1941 2,344,266 Reissner Mar. 14, 1944 2,364,871 Reissner Dec. 12, 1944 2,365,214 Reissner Dec. 19, 1944 2,566,884 Hackenthall et al. Sept. 4, 1951 FOREIGN PATENTS Number Country Date 161,961 Great Britain May 6, 1918 238,566 Switzerland Nov. 1, 1945 

